Na+/K+:H+ antiporter, Nhe-7, present in the Golgi apparatus and endosomes. There are four isoforms, NHE6-9. They regulate the luminal pH as well as intracellular trafficking, and function in cell polarity development (Ohgaki et al., 2011). Nhe-6 (Nhe6) is associated with X-linked intellectural disability and autism when processing and trafficking is impaired (Ilie et al. 2013).

Sodium/hydrogen exchanger 6 (Na+/H+ exchanger 6) (NHE-6) (Solute carrier family 9 member 6). This Na+/H+ exchanger is encoded by an X-linked gene that is widely
expressed and especially abundant in brain, heart and skeletal muscle
where it is implicated in endosomal pH homeostasis and trafficking as well as maintenance of cell polarity. Several mutations in the coding
region of NHE6 are linked with severe intellectual disability,
autistic behavior, ataxia and other abnormalities (Ilie et al. 2014). A christianson syndrome-linked mutation disrupts endosomal function and elicits neurodegeneration and cell death (Ilie et al. 2016). Heterozygous female mice suffer from visuospatial memory and motor
coordination deficits similar to but less severe than those observed in X-chromosome hemizygous
mutant males (Sikora et al. 2016).

Endomembrane (Golgi) K+, Na+/H+ exchanger 5, NHX5, of 521 aas and 11 TMSs. Three acidic residues are critical for transport activity as well as seedling growth, regulation of protein transport into vesicles and ionic homeostasis (Qiu 2016). NHX6 is 80% identical to NHX5 (535 aas and 11 TMSs) and serves the same function.

Sodium:proton antiporter of 468 aas and 13 TMSs, Sod2 or NHE1. Residues within TMS 11 play important roles in transport, suggesting that this TMS forms part of the ion translocation core (Dutta et al. 2017).

Na+:H+ antiporter, Nhx1 of 470 aas and 9 TMSs. NHX1 can confer a high level of salinity tolerance when
overexpressed in Brassica juncea. Verma et al. 2007 reported its functional characterization. Overexpression conferred a high level of salinity tolerance in rice.
Transgenic rice plants overexpressing PgNHX1 developed more extensive root systems and completed
their life cycle by setting flowers and seeds in the presence of 150 mM NaCl.

Na+/H+ antiporter 1 (MjNhaP1). NhaP1 is a dimer with 13 TMSs per monomer as revealed by electron crystalography of 2-d crystals (Goswami et al. 2011). This structure is contrasted with that of the distantly related bacterial NhaA; these two structures are quite different in detail, but similar within the 6 TMS repeat unit. Asp234/235 of helix VIII are involved in ligand-binding, and
helix X plays a role in the activation of the transporter (Kedrov et al. 2007).

Na+/H+ antiporter, NhaP, of 443 aas. Several 3-d structures are known (Wöhlert et al. 2014). The ion is coordinated by three acidic side chains, a water molecule, a
serine and a main-chain carbonyl in an unwound stretch of TMS 5 at the deepest point of a negatively charged
cytoplasmic funnel. A second narrow polar channel may facilitate proton uptake from the cytoplasm. Transport activity is cooperative
at pH 6 but not at pH 5, due to pH-dependent allosteric
coupling of protomers through two histidines at the dimer interface (Wöhlert et al. 2014).

ApNhaP: a Na+:H+ antiporter at pH 5-9; a Ca2+:H+ antiporter at alkaline pH (not an Li:H+ antiporter) (Waditee et al. 2001). When the gene for ApNhaP is expressed in the fresh water cyanobacterium, Synechococcus sp. PCC 7942, it became salt tolerant and could live in salt water (Waditee et al. 2002; ).

Testis-specific sodium:proton exchanger, mtsNHE (Slc9c1) of 1175 aas and 12 - 16 TMSs. It is present in sperm flagellae and seems to be required for optimal sperm motility, fertilization and the acrosome reaction (Liu et al. 2010). 69% identical to the human NHE, TC# 2.A.36.7.5. It may have a 12 TMS topology, but has a long C-terminal hydrophilic domain with a segment showing 2 - 4 TMSs.